1. Field of the Invention
The present invention relates to a method of forming a foamed gasket applied on a sealing surface of various kinds of articles, such as waterproof cases for containing electronic parts etc. of cars, head lights of cars, lids of various containers and the like, and more particularly, a method of forming a foamed gasket in which expandable materials of two-liquid types are used as raw materials which are long in pot life, short in curing time and high in the rate of closed cells, and in which these two liquids may be homogeneously and rapidly mixed by a simple step, and thus becoming excellent in workability and capable of applying to on-line systems.
2. Description of the Prior Art
On the sealing surfaces of waterproof cases of cars, head-lights or lids of various containers, foamed gaskets are formed.
Exemplarily, on the contacting part between the body and the lid of the waterproof case, such as on the sealing groove as indicated in FIG. 1, moreover, on the contacting part between the body and the glass cap of the head light, such as on the sealing groove of the body as indicated in FIG. 3, and furthermore, on the contacting part between the lid and the body of the various containers, foamed gaskets are formed by on-line gasket system (OLGS), respectively.
In the past, urethane foams have been used as the afore-mentioned foamed gasket.
However, it is feared that the urethane foams are gelled in the mixing chamber since the pot life of the urethane foams is short at several seconds to 2 minutes, and thus, the mixing of the main agent and the curing agent becomes difficult in the on-line system, and moreover, it is difficult to keep the shapes unchanged between the starting time and the ending time of the coatings since the reaction thereof immediately starts after the coating, and furthermore, it is necessary to prepare spaces for curing since the curing time is long at 60 minutes to 24 hours, and accordingly, it can be said that it is difficult to mix them homogeneously and rapidly with a simple step, and thus, they become inferior in workability. Moreover, the rate of closed cells thereof is low at below 20 percent, and thus, the sealing level becomes inferior, and further, the heatproof temperature is low in the range from -20.degree. to 100.degree. C., and thus, the availability thereof becomes limited.
Therefore, the afore-mentioned urethane foams can only be used limitedly with the parts in which the sealing grooves are large or the high gasket efficiency is not required.